Epidemiological data support the hypothesis that ovarian cancers may be an endocrine-related tumor. However, the role hormone regulated genes in ovarian carcinogenesis has not been extensively studied. SPARC, also termed osteonectin, BM-40, and 43K protein, is an acidic, cysteine-rich component of the extracellular matrix that displays a high degree of interspecies sequence conservation and has been shown to be directly regulated by progesterone and dexamethasone and indirectly by cytokines. The experiments outlined in this proposal will test the hypothesis that this progesterone regulated glycoprotein SPARC is a physiologic regulator of ovarian surface epithelial cell function and deregulation of SPARC plays a role in ovarian carcinogenesis. We have cloned the SPARC gene from the normal ovarian epithelial cells and demonstrated that it is expressed at high levels in the human normal ovarian surface epithelial (HOSE) cells and at much lower levels in ovarian carcinoma cells in vitro and in vivo. Our data show that there is a tight correlation between SPARC expression in normal and neoplastic cell in vitro and in vivo and suggest that SPARC may play an important role in ovarian epithelial cell growth and differentiation. Based on these preliminary data, we propose (I). To study the expression pattern of the SPARC gene in normal ovary and ovarian tumor tissues of different stages and histological grades by Northern and Western blot analysis, in-situ hybridization and immunohistochemical detection: (2). To quantify the amount of biological active SPARC secreted by normal HOSE cells and the ovarian carcinoma cells by cell spreading assay and Northern and Western Blot analysis: and to characterize the biological effects of SPARC on these cells by [3H]-thymidine incorporation study and basement membrane invasion assay; and (3). To genetically alter SPARC expression in normal HOSE cells and ovarian carcinoma cells by transfection of full length anti-sense and sense SPARC cDNA in expression vector in order to test the hypothesis that expression of SPARC in ovarian carcinoma cells alters malignant properties such as tumor growth and invasion in vitro and in vivo . If SPARC is identified as an important regulator of ovarian epithelial cell function and up-regulation of the protein in ovarian carcinoma cells can inhibit their growth, this may suggest that strategies based on alteration in SPARC expression may have therapeutic potential in ovarian malignancies.